The present invention relates to an authentication system and more particularly, to an authentication system having an electric field sensor.
Nowadays, authentication systems are used in various types of devices. An authentication system authenticates a subject product that is connected to or used in a main body of a device to determine whether the subject product is authentic or authorized. The connection of an unauthentic subject product to the main body may result in erroneous operation, undesirable heating, or failure of the device. In addition to causing device failure, copyrights may be infringed if the use of the subject product is prohibited by copyright.
FIG. 1 is a block diagram showing a conventional authentication system 100 applied to a mobile phone MP100. The authentication system 100 performs authentication between a main body M100 (in this case, a battery charger) and a battery pack B100, which is connected to the main body M100. The battery pack B100 includes a power switch B14 arranged between a rechargeable battery B12 and a terminal T1 of the battery pack B100. The battery charger (main body M100) includes an internal circuit M12, which functions as a charging circuit, and a power switch M14, which is arranged between the internal circuit M12 and a terminal T2 of the main body M100. Connection of the battery pack B100 to the main body M100 connects the two power switches B14 and M14 to each other via the terminals T1 and T2. In such a state, when the power switches B14 and M14 are both activated, a charging path is formed between the rechargeable battery B12 and the internal circuit M12 so that the rechargeable battery B12 becomes rechargeable through the charging path.
The conventional authentication system 100 includes a host processor 112, which is arranged in the main body M100, and an authentication IC 114, which is arranged in the battery pack B100. Connection of the battery pack B100 to the main body M100 connects the host processor 112 and the authentication IC 114 to each other via a terminal T3 of the main body M100 and a terminal T4 of the battery pack B100. The host processor 112 stores a main body key K1, and the authentication IC 114 stores a product key K2. Japanese Laid-Open Patent Publication No. 2000-76063 describes a prior art authentication system that is similar to the authentication system 100 of FIG. 1.
In the authentication operation performed in the prior art system described above, the host processor 112 receives the product key K2 from the authentication IC114 and determines whether or not the product key K2 is authentic. If the received product key K2 is authentic, the host processor 112 activates the power switch M14. In the same manner, the authentication IC 114 receives the main body key K1 from the host processor 112 and determines whether or not the received main body key K1 is authentic. If the received main body key K1 is authentic, the authentication IC activates the power switch B14. When authentication cannot be established, either one of the power switches B14 and M14 is not activated. This prohibits charging.
In the conventional authentication system 100, authentication of the subject product (battery pack B100) requires electrical communication through a current path formed between the host processor 112 and the authentication IC 114. The electrical communication consumes power. In portable electronic equipment such as the mobile phone MP100, the authentication process uses the power of the rechargeable battery B12. However, the authentication process is not an essential operation of a device (here, the mobile phone) that implements the functions for performing the authentication process. Accordingly, there is a demand for reduction in the power consumed by the authentication process. Further, for quick activation of the device, it is desirable that the time required for authentication be shortened. However, in the authentication system 100 of the prior art, the requirement for electrical communication (mutual communication) between the host processor 112 and the authentication IC acts as a bottle neck that hinders shortening of the authentication time.